Compositions comprising tetrafluoropropene and tetrafluoroethane; their use in power cycles; and power cycle apparatus

ABSTRACT

A method for converting heat from a heat source to mechanical energy is provided. The method comprises heating a working fluid E-1,3,3,3-tetrafluoropropene and at least one compound selected from 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane using heat supplied from the heat source; and expanding the heated working fluid to lower the pressure of the working fluid and generate mechanical energy as the pressure of the working fluid is lowered. Additionally, a power cycle apparatus containing a working fluid to convert heat to mechanical energy is provided. The apparatus contains a working fluid comprising E-1,3,3,3-tetrafluoropropene and at least one compound selected from 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane. A working fluid is provided comprising an azeotropic or azeotrope-like combination of E-1,3,3,3-tetrafluoropropene, 1,1,2,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane.

FIELD OF THE INVENTION

This invention relates to methods and systems having utility in numerousapplications, and in particular, in power cycles, such as organicRankine cycles.

BACKGROUND OF THE INVENTION

Low global warming potential working fluids are needed for power cyclessuch as organic Rankine cycles. Such materials must have lowenvironmental impact, as measured by low global warming potential andlow or zero ozone depletion potential.

SUMMARY OF THE INVENTION

The present invention involves a composition comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least onetetrafluoroethane, 1,1,2,2-tetrafluoroethane (HFC-134) or1,1,1,2-tetrafluoroethane (HFC-134a) as described in detail herein.

In accordance with this invention, a method is provided for convertingheat from a heat source to mechanical energy. The method comprisesheating a working fluid comprising E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze) and at least one compound selected from1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a) using heat supplied from a heat source; and expanding theheated working fluid to lower the pressure of the working fluid andgenerate mechanical energy as the pressure of the working fluid islowered.

In accordance with this invention, a power cycle apparatus containing aworking fluid to convert heat to mechanical energy is provided. Theapparatus contains a working fluid comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a).

In accordance with this invention, a working fluid is providedcomprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze),1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a heat source and an organic Rankine cyclesystem in direct heat exchange according to the present invention.

FIG. 2 is a block diagram of a heat source and an organic Rankine cyclesystem which uses a secondary loop configuration to provide heat from aheat source to a heat exchanger for conversion to mechanical energyaccording to the present invention.

FIG. 3 is a plot of the vapor pressure of a composition containingE-HFO-1234ze and HFC-134 as compared to the vapor pressure of HFC-134a.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before addressing details of embodiments described below, some terms aredefined or clarified.

Global warming potential (GWP) is an index for estimating relativeglobal warming contribution due to atmospheric emission of a kilogram ofa particular greenhouse gas compared to emission of a kilogram of carbondioxide. GWP can be calculated for different time horizons showing theeffect of atmospheric lifetime for a given gas. The GWP for the 100 yeartime horizon is commonly the value referenced.

Net cycle power output is the rate of mechanical work generation at theexpander (e.g., a turbine) less the rate of mechanical work consumed bythe compressor (e.g., a liquid pump).

Volumetric capacity for power generation is the net cycle power outputper unit volume of working fluid (as measured at the conditions at theexpander outlet) circulated through the power cycle (e.g., organicRankine cycle).

Cycle efficiency (also referred to as thermal efficiency) is the netcycle power output divided by the rate at which heat is received by theworking fluid during the heating stage of a power cycle (e.g., organicRankine cycle).

Subcooling is the reduction of the temperature of a liquid below thatliquid's saturation point for a given pressure. The saturation point isthe temperature at which a vapor composition is completely condensed toa liquid (also referred to as the bubble point). But subcoolingcontinues to cool the liquid to a lower temperature liquid at the givenpressure. Subcool amount is the amount of cooling below the saturationtemperature (in degrees) or how far below its saturation temperature aliquid composition is cooled.

Superheat is a term that defines how far above its saturation vaportemperature of a vapor composition is heated. Saturation vaportemperature is the temperature at which, if the composition is cooled,the first drop of liquid is formed, also referred to as the “dew point”.

Temperature glide (sometimes referred to simply as “glide”) is theabsolute value of the difference between the starting and endingtemperatures of a phase-change process by a refrigerant within acomponent of a refrigerant system, exclusive of any subcooling orsuperheating. This term may be used to describe condensation orevaporation of a near azeotrope or non-azeotropic composition. Averageglide refers to the average of the glide in the evaporator and the glidein the condenser of a specific chiller system operating under a givenset of conditions.

An azeotropic composition is a mixture of two or more differentcomponents which, when in liquid form under a given pressure, will boilat a substantially constant temperature, which temperature may be higheror lower than the boiling temperatures of the individual components, andwhich will provide a vapor composition essentially identical to theoverall liquid composition undergoing boiling. (see, e.g., M. F. Dohertyand M. F. Malone, Conceptual Design of Distillation Systems, McGraw-Hill(New York), 2001, 185-186, 351-359).

Accordingly, the essential features of an azeotropic composition arethat at a given pressure, the boiling point of the liquid composition isfixed and that the composition of the vapor above the boilingcomposition is essentially that of the overall boiling liquidcomposition (i.e., no fractionation of the components of the liquidcomposition takes place). It is also recognized in the art that both theboiling point and the weight percentages of each component of theazeotropic composition may change when the azeotropic composition issubjected to boiling at different pressures. Thus, an azeotropiccomposition may be defined in terms of the unique relationship thatexists among the components or in terms of the compositional ranges ofthe components or in terms of exact weight percentages of each componentof the composition characterized by a fixed boiling point at a specifiedpressure.

For the purpose of this invention, an azeotrope-like composition means acomposition that behaves substantially like an azeotropic composition(i.e., has constant boiling characteristics or a tendency not tofractionate upon boiling or evaporation). Hence, during boiling orevaporation, the vapor and liquid compositions, if they change at all,change only to a minimal or negligible extent. This is to be contrastedwith non-azeotrope-like compositions in which during boiling orevaporation, the vapor and liquid compositions change to a substantialdegree.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a composition,process, method, article, or apparatus that comprises a list of elementsis not necessarily limited to only those elements but may include otherelements not expressly listed or inherent to such composition, process,method, article, or apparatus. Further, unless expressly stated to thecontrary, “or” refers to an inclusive or and not to an exclusive or. Forexample, a condition A or B is satisfied by any one of the following: Ais true (or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

The transitional phrase “consisting of” excludes any element, step, oringredient not specified. If in the claim such would close the claim tothe inclusion of materials other than those recited except forimpurities ordinarily associated therewith. When the phrase “consistsof” appears in a clause of the body of a claim, rather than immediatelyfollowing the preamble, it limits only the element set forth in thatclause; other elements are not excluded from the claim as a whole.

The transitional phrase “consisting essentially of” is used to define acomposition, method or apparatus that includes materials, steps,features, components, or elements, in addition to those literallydisclosed provided that these additional included materials, steps,features, components, or elements do materially affect the basic andnovel characteristic(s) of the claimed invention. The term ‘consistingessentially of’ occupies a middle ground between “comprising” and‘consisting of’.

Where applicants have defined an invention or a portion thereof with anopen-ended term such as “comprising,” it should be readily understoodthat (unless otherwise stated) the description should be interpreted toalso describe such an invention using the terms “consisting essentiallyof” or “consisting of.”

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze, E-CHF═CHCF₃) is availablecommercially from fluorocarbon manufacturers or may be made by methodsknown in the art. In particular, this compound may be prepared bydehydrofluorination of a group of pentafluoropropanes, including1,1,1,2,3-pentafluoropropane (HFC-245eb, CF₃CHFCH₂F),1,1,1,3,3-pentafluoropropane (HFC-245fa, CF₃CH₂CHF₂). Thedehydrofluorination reaction may take place in the vapor phase in thepresence or absence of catalyst, and also in the liquid phase byreaction with caustic, such as NaOH or KOH. These reactions aredescribed in more detail in U.S. Patent Publication No. 2006/0106263,incorporated herein by reference.

1,1,1,2-tetrafluoroethane (HFC-134a, CF₃CH₂F) is available availablecommercially from many refrigerant producers and distributors or may beprepared by methods known in the art. HFC-134a may be made by thehydrogenation of 1,1-dichloro-1,1,1,2-tetrafluoroethane (i.e., CCl₂FCF₃or CFC-114a) to 1,1,1,2-tetrafluoroethane. Additionally,1,1,2,2-tetrafluoroethane (HFC-134, CHF₂CHF₂) may be made by thehydrogenation of 1,2-dichloro-1,1,2,2-tetrafluoroethane (i.e.,CCIF₂CCIF₂ or CFC-114) to 1,1,2,2-tetrafluoroethane.

Power Cycle Methods

Heat at temperatures up to about 100° C. is abundantly available fromvarious sources. It can be captured as a byproduct from variousindustrial processes, it can be collected from solar irradiation throughsolar panels or it can be extracted from geological hot water reservoirsthrough shallow or deep wells. Such heat can be converted to mechanicalor electrical power for various uses through Rankine cycles usingworking fluids comprising E-HFO-1234ze and HFC-134 or working fluidscomprising E-HFO-1234ze, HFC-134, and HFC-134a.

A sub-critical organic Rankine cycle (ORC) is defined as a Rankine cyclein which the organic working fluid used in the cycle receives heat at apressure lower than the critical pressure of the organic working fluidand the working fluid remains below its critical pressure throughout theentire cycle.

A trans-critical ORC is defined as a Rankine cycle in which the organicworking fluid used in the cycle receives heat at a pressure higher thanthe critical pressure of the organic working fluid. In a trans-criticalcycle, the working fluid is not at a pressure higher than its criticalpressure throughout the entire cycle.

A super-critical power cycle is defined as a power cycle which operatesat pressures higher than the critical pressure of the organic workingfluid used in the cycle and involves the following steps: compression;heating; expansion; cooling.

In accordance with this invention, a method is provided for convertingheat from a heat source to mechanical energy. The method comprisesheating a working fluid using heat supplied from the heat source; andexpanding the heated working fluid to lower the pressure of the workingfluid and generate mechanical energy as the pressure of the workingfluid is lowered. The method is characterized by using a working fluidcomprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least onecompound selected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a). In another embodiment, the methodis characterized by using a working fluid comprising E-HFO-1234ze andHFC-134 or a working fluid comprising E-HFO-1234ze, HFC-134, andHFC-134a.

The method of this invention is typically used in an organic Rankinepower cycle. Heat available at relatively low temperatures compared tosteam (inorganic) power cycles can be used to generate mechanical powerthrough Rankine cycles using working fluids comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a). In the method of this invention,working fluid comprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) andat least one compound selected from 1,1,2,2-tetrafluoroethane (HFC-134)and 1,1,1,2-tetrafluoroethane (HFC-134a) is compressed prior to beingheated. Compression may be provided by a pump which pumps working fluidto a heat transfer unit (e.g., a heat exchanger or an evaporator) whereheat from the heat source is used to heat the working fluid. The heatedworking fluid is then expanded, lowering its pressure. Mechanical energyis generated during the working fluid expansion using an expander.Examples of expanders include turbo or dynamic expanders, such asturbines, and positive displacement expanders, such as screw expanders,scroll expanders, and piston expanders. Examples of expanders alsoinclude rotary vane expanders (Musthafah b. Mohd. Tahir, Noboru Yamada,and Tetsuya Hoshino, International Journal of Civil and EnvironmentalEngineering 2:1 2010).

Mechanical power can be used directly (e.g. to drive a compressor) or beconverted to electrical power through the use of electrical powergenerators. In a power cycle where the working fluid is re-used, theexpanded working fluid is cooled. Cooling may be accomplished in aworking fluid cooling unit (e.g. a heat exchanger or a condenser). Thecooled working fluid can then be used for repeated cycles (i.e.,compression, heating, expansion, etc.). The same pump used forcompression may be used for transferring the working fluid from thecooling stage.

In one embodiment, the method for converting heat to mechanical energyuses a working fluid comprising E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze) and at least one compound selected from1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a).

Of note in the method for converting heat to mechanical energy areworking fluids that consist essentially E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze) and 1,1,2,2-tetrafluoroethane (HFC-134). Also of note inthe method for converting heat to mechanical energy are working fluidsconsisting essentially of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze),1,1,2,2-tetrafluoroethane (HFC-134), and 1,1,1,2-tetrafluoroethane(HFC-134a). Also of note are methods for converting heat from a heatsource to mechanical energy wherein the working fluid comprises orconsists essentially of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,2,2-tetrafluoroethane (HFC-134). In another embodiment of the methodfor converting heat to mechanical energy, the working fluid consists ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,2,2-tetrafluoroethane (HFC-134). Also of note are methods forconverting heat from a heat source to mechanical energy wherein theworking fluid comprises or consists essentially ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,1,2-tetrafluoroethane (HFC-134a). In another embodiment of themethod for converting heat to mechanical energy, the working fluidconsists of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,1,2-tetrafluoroethane (HFC-134a).

Of note for use in power cycle apparatus are compositions comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) that are non-flammable. Certaincompositions comprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) andat least one compound selected from 1,1,2,2-tetrafluoroethane (HFC-134)and 1,1,1,2-tetrafluoroethane (HFC-134a) are non-flammable by standardtest ASTM 681. It is expected that certain compositions comprisingE-HFO-1234ze and HFC-134 and/or HFC-134a are non-flammable by standardtest ASTM 681. Of particular note are compositions containingE-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 85 weightpercent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 84weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 83weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 82weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 81weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 80weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 78weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 76weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a with no more than 74weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a no more than 72weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 and/or HFC-134a no more than 70weight percent E-HFO-1234ze. Also of particular note are compositionscontaining E-HFO-1234ze and HFC-134 with no more than 69 weight percentE-HFO-1234ze. Therefore, of particular note are compositions containingfrom about 1 weight percent to 69 weight percent E-HFO-1234ze and about99 weight percent to 31 weight percent HFC-134. Also of particular noteare compositions containing E-HFO-1234ze and HFC-134a with no more than85 weight percent E-HFO-1234ze. Therefore, of particular note arecompositions containing from about 1 weight percent to 85 weight percentE-HFO-1234ze and about 99 weight percent to 15 weight percent HFC-134a.Additionally, of particular note are compositions containing from about55 weight percent to about 81 weight percent E-HFO-1234ze and about 45weight percent to about 18 weight percent HFC-134a. Further, ofparticular note are compositions containing from about 55 weight percentto about 70 weight percent E-HFO-1234ze and about 45 weight percent toabout 30 weight percent HFC-134a. Also of particular note are azeotropicand azeotrope-like compositions comprising E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze) and at least one compound selected from1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a). In particular, azeotrope-like compositions containing fromabout 1 to about 99 weight percent E-1,3,3,3-tetrafluoropropene and fromabout 99 to about 1 weight percent HFC-134 or azeotrope-likecompositions containing from about 1 to about 99 weight percentE-1,3,3,3-tetrafluoropropene and from about 99 to about 1 weight percentHFC-134a.

Of particular utility in the method converting heat to mechanical energyare those embodiments wherein the working fluid consists essentially ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a). Also of particular utility arethose embodiments wherein the working fluid consists ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) 1,1,2,2-tetrafluoroethane(HFC-134). Also of particular utility are those embodiments wherein theworking fluid consists of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze),1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a).

Of particular note, for use in the method converting heat to mechanicalenergy, are compositions containing from about 35 to about 95 weightpercent E-1,3,3,3-tetrafluoropropene and from about 5 to about 65 weightpercent HFC-134. Also of particular note, for use in the methodconverting heat to mechanical energy, are azeotropic and azeotrope-likecompositions containing from about 5 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from about 5 to about 95 weight percentHFC-134. Also of particular note, for use in the method converting heatto mechanical energy, are azeotropic and azeotrope-like compositionscontaining from about 5 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from about 40 to about 95 weightpercent HFC-134. Also of particular note, for use in the methodconverting heat to mechanical energy, are azeotropic and azeotrope-likecompositions containing from about 35 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from about 40 to about 65 weightpercent HFC-134. Also of particular note, for use in the methodconverting heat to mechanical energy, are azeotropic and azeotrope-likecompositions containing from about 63 to about 75 weight percentE-1,3,3,3-tetrafluoropropene and from about 37 to about 25 weightpercent HFC-134.

Also of particular note, for use in the method converting heat tomechanical energy, are compositions containing from about 35 to about 95weight percent E-1,3,3,3-tetrafluoropropene and from about 5 to about 65weight percent total of HFC-134 and HFC-134a. Also of particular note,for use in the method converting heat to mechanical energy, areazeotropic and azeotrope-like compositions containing from about 5 toabout 95 weight percent E-1,3,3,3-tetrafluoropropene and from about 5 toabout 95 weight percent total of HFC-134 and HFC-134a. Also ofparticular note, for use in the method converting heat to mechanicalenergy, are azeotropic and azeotrope-like compositions containing fromabout 5 to about 60 weight percent E-1,3,3,3-tetrafluoropropene and fromabout 40 to about 95 weight percent total of HFC-134 and HFC-134a.

Also of particular note, for use in the method converting heat tomechanical energy, are azeotropic and azeotrope-like compositionscontaining from about 35 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from about 5 to about 65 weight percenttotal of HFC-134 and HFC-134a. Also of particular note, for use in themethod converting heat to mechanical energy, are azeotropic andazeotrope-like compositions containing from about 35 to about 60 weightpercent E-1,3,3,3-tetrafluoropropene and from about 40 to about 65weight percent total of HFC-134 and HFC-134a.

For compositions useful in the method for converting heat to mechanicalenergy, are compositions containing E-1,3,3,3-tetrafluoropropene,HFC-134, and HFC-134a. In particular, of note are compositionscomprising from about 5 to about 95 weight percentE-1,3,3,3-tetrafluoropropene, from about 5 to about 95 weight percent ofHFC-134 and from about 5 to about 95 weight percent of HFC-134a. Also ofnote are compositions comprising from about 35 to about 95 weightpercent E-1,3,3,3-tetrafluoropropene, from about 2 to about 38 weightpercent of HFC-134 and from about 2 to about 39 weight percent ofHFC-134a. Also of note are compositions comprising from about 35 toabout 60 weight percent E-1,3,3,3-tetrafluoropropene, from about 10 toabout 26 weight percent of HFC-134 and from about 24 to about 49 weightpercent of HFC-134a. Also of note are compositions comprising from about5 to about 60 weight percent E-1,3,3,3-tetrafluoropropene, from about 10to about 38 weight percent of HFC-134 and from about 24 to about 72weight percent of HFC-134a.

Also of particular utility for use in the method converting heat tomechanical energy are those embodiments wherein the working fluid has alow GWP. For GWP less than 1000, compositions containing E-HFO-1234zeand HFC-134 comprise from 11 weight percent to 99 weight percentE-HFO-1234ze and 89 weight percent to 1 weight percent HFC-134. For GWPless than 1000, compositions containing E-HFO-1234ze and HFC-134acomprise from 30.5 weight percent to 99 weight percent E-HFO-1234ze and69.5 weight percent to 1 weight percent HFC-134a.

For GWP less than 500, compositions containing E-HFO-1234ze and HFC-134comprise from 56 weight percent to 99 weight percent E-HFO-234ze and 44weight percent to 1 weight percent HFC-134. For GWP less than 500,compositions containing E-HFO-1234ze and HFC-134a comprise from 65.5weight percent to 99 weight percent E-HFO-1234ze and 34.5 weight percentto 1 weight percent HFC-134a.

For GWP less than 150, compositions containing E-HFO-1234ze and HFC-134comprise from 87.5 weight percent to 99 weight percent E-HFO-1234ze and12.5 weight percent to 1 weight percent HFC-134. For GWP less than 150,compositions containing E-HFO-1234ze and HFC-134a comprise from 90weight percent to 99 weight percent E-HFO-1234ze and 10 weight percentto 1 weight percent HFC-134a.

In one embodiment, the present invention relates to a method forconverting heat from a heat source to mechanical energy using asub-critical cycle. This method comprises the following steps:

-   -   (a) compressing a liquid working fluid to a pressure below its        critical pressure;    -   (b) heating compressed liquid working fluid from (a) using heat        supplied by the heat source to form vapor working fluid;    -   (c) expanding heated working fluid from (b) to lower the        pressure of the working fluid and generate mechanical energy;    -   (d) cooling expanded working fluid from (c) to form a cooled        liquid working fluid; and    -   (e) cycling cooled liquid working fluid from (d) to (a) for        compression.

In the first step of the sub-critical Organic Rankine Cycle (ORC)system, described above, the working fluid in liquid phase comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) is compressed to above its criticalpressure. In a second step, said working fluid is passed through a heatexchanger to be heated to a higher temperature before the fluid entersthe expander wherein said heat exchanger is in thermal communicationwith said heat source. The heat exchanger receives heat energy from theheat source by any known means of thermal transfer. The ORC systemworking fluid circulates through the heat supply heat exchanger where itgains heat.

Embodiments including use of one or more internal heat exchangers (e.g.,a recuperator), and/or use of more than one cycle in a cascade systemare intended to fall within the scope of the sub-critical ORC powercycles of the present invention.

In one embodiment, the present invention relates to a method forconverting heat from a heat source to mechanical energy using atrans-critical cycle. This method comprises the following steps:

-   -   (a) compressing a liquid working fluid above said working        fluid's critical pressure;    -   (b) heating compressed working fluid from (a) using heat        supplied by the heat source;    -   (c) expanding heated working fluid from (b) to lower the        pressure of the working fluid below its critical pressure and        generate mechanical energy;    -   (d) cooling expanded working fluid from (c) to form a cooled        liquid working fluid; and    -   (e) cycling cooled liquid working fluid from (d) to (a) for        compression.

In the first step of the trans-critical Organic Rankine Cycle (ORC)system, described above, the working fluid in liquid phase comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) is compressed to above its criticalpressure. In a second step, said working fluid is passed through a heatexchanger to be heated to a higher temperature before the fluid entersthe expander wherein said heat exchanger is in thermal communicationwith said heat source. The heat exchanger receives heat energy from theheat source by any known means of thermal transfer. The ORC systemworking fluid circulates through the heat supply heat exchanger where itgains heat.

In the next step, at least a portion of the heated working fluid isremoved from said heat exchanger and is routed to the expander where theexpansion process results in conversion of at least portion of the heatenergy content of the working fluid into mechanical shaft energy. Theshaft energy can be used to do any mechanical work by employingconventional arrangements of belts, pulleys, gears, transmissions orsimilar devices depending on the desired speed and torque required. Inone embodiment, the shaft can also be connected to an electricpower-generating device such as an induction generator. The electricityproduced can be used locally or delivered to the grid. The pressure ofthe working fluid is reduced to below critical pressure of said workingfluid, thereby producing vapor phase working fluid.

In the next step, the working fluid is passed from the expander to acondenser, wherein the vapor phase working fluid is condensed to produceliquid phase working fluid. The above steps form a loop system and canbe repeated many times.

Embodiments including use of one or more internal heat exchangers (e.g.,a recuperator), and/or use of more than one cycle in a cascade systemare intended to fall within the scope of the trans-critical ORC powercycles of the present invention.

Additionally, for a trans-critical organic Rankine cycle, there areseveral different modes of operation.

In one mode of operation, in the first step of a trans-critical organicRankine cycle, the working fluid is compressed above the criticalpressure of the working fluid substantially isentropically. In the nextstep, the working fluid is heated under a constant pressure (isobaric)condition to above its critical temperature. In the next step, theworking fluid is expanded substantially isentropically at a temperaturethat maintains the working fluid in the vapor phase. At the end of theexpansion the working fluid is a superheated vapor at a temperaturebelow its critical temperature. In the last step of this cycle, theworking fluid is cooled and condensed while heat is rejected to acooling medium. During this step the working fluid condensed to aliquid. The working fluid could be subcooled at the end of this coolingstep.

In another mode of operation of a trans-critical ORC power cycle, in thefirst step, the working fluid is compressed above the critical pressureof the working fluid, substantially isentropically. In the next step theworking fluid is then heated under a constant pressure condition toabove its critical temperature, but only to such an extent that in thenext step, when the working fluid is expanded substantiallyisentropically, and its temperature is reduced, the working fluid isclose enough to the conditions for a saturated vapor that partialcondensation or misting of the working fluid may occur. At the end ofthis step, however, the working fluid is still a slightly superheatedvapor. In the last step, the working fluid is cooled and condensed whileheat is rejected to a cooling medium. During this step the working fluidcondensed to a liquid. The working fluid could be subcooled at the endof this cooling/condensing step.

In another mode of operation of a trans-critical ORC power cycle, in thefirst step, the working fluid is compressed above the critical pressureof the working fluid, substantially isentropically. In the next step,the working fluid is heated under a constant pressure condition to atemperature either below or only slightly above its criticaltemperature. At this stage, the working fluid temperature is such thatwhen the working fluid is expanded substantially isentropically in thenext step, the working fluid is partially condensed. In the last step,the working fluid is cooled and fully condensed and heat is rejected toa cooling medium. The working fluid could be subcooled at the end ofthis step.

While the above embodiments for a trans-critical ORC cycle showsubstantially isentropic expansions and compressions, and isobaricheating or cooling, other cycles wherein such isentropic or isobaricconditions are not maintained but the cycle is neverthelessaccomplished, are within the scope of the present invention.

In one embodiment, the present invention relates to a method forconverting heat from a heat source to mechanical energy using asuper-critical cycle. This method comprises the following steps:

-   -   (a) compressing a working fluid from a pressure above its        critical pressure to a higher pressure;    -   (b) heating compressed working fluid from (a) using heat        supplied by the heat source;    -   (c) expanding heated working fluid from (b) to lower the        pressure of the working fluid to a pressure above its critical        pressure and generate mechanical energy;    -   (d) cooling expanded working fluid from (c) to form a cooled        working fluid above its critical pressure; and    -   (e) cycling cooled liquid working fluid from (d) to (a) for        compression.

Embodiments including use of one or more internal heat exchangers (e.g.,a recuperator), and/or use of more than one cycle in a cascade systemare intended to fall within the scope of the super-critical ORC powercycles of the present invention.

Typically, in the case of sub-critical Rankine cycle operation, most ofthe heat supplied to the working fluid is supplied during theevaporation of the working fluid. As a result the working fluidtemperature is essentially constant during the transfer of heat from theheat source to the working fluid. In contrast, the working fluidtemperature can vary when the fluid is heated isobarically without phasechange at a pressure above its critical pressure. Accordingly, when theheat source temperature varies, the use of a fluid above its criticalpressure to extract heat from a heat source allows better matchingbetween the heat source temperature and the working fluid temperaturecompared to the case of sub-critical heat extraction. As a result, theefficiency of the heat exchange process in a super-critical cycle or atrans-critical cycle is often higher than that of the sub-critical cycle(see Chen et al, Energy, 36, (2011) 549-555 and references therein).

The critical temperature and pressure of E-1,3,3,3-tetrafluoropropeneare 109.4° C. and 3.63 MPa, respectively. The critical temperature andpressure of HFC-134a are 101.1° C. and 4.06 MPa, respectively. Thecritical temperature and pressure of HFC-134 are 118.6° C. and 4.62 MPa,respectively. Use of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and atleast one compound selected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) as a working fluid can enable

Rankine cycles that receive heat from heat sources with temperatureshigher than the critical temperature thereof in a super-critical cycleor a trans-critical cycle. Higher temperature heat sources can lead tohigher cycle energy efficiencies and volumetric capacities for powergeneration (relative to lower temperature heat sources). When heat isreceived using a working fluid above its critical temperature, a fluidheater having a specified pressure and exit temperature (essentiallyequal to the expander inlet temperature) is used instead of theevaporator (or boiler) used in the conventional sub-critical Rankinecycle.

In one embodiment of the above methods, the efficiency of convertingheat to mechanical energy (cycle efficiency) is at least about 2%. In asuitable embodiment, the efficiency can be selected from the following:

-   -   about 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9,        9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5,        16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22,        22.5, 23, 23.5, 24, 24.5, and about 25%.

In another embodiment, the efficiency is selected from a range that hasendpoints (inclusive) as any two efficiency numbers supra.

Typically for sub-critical cycles, the temperature to which the workingfluid is heated using heat from the heat source is in the range of fromabout 50° C. to less than the critical temperature of the working fluid,preferably from about 80° C. to less than the critical temperature ofthe working fluid, more preferably from about 95° C. to less than thecritical temperature of the working fluid. Typically for trans-criticaland super-critical cycles, the temperature to which the working fluid isheated using heat from the heat source is in the range of from above thecritical temperature of the working fluid to about 400° C., preferablyfrom above the critical temperature of the working fluid to about 300°C., more preferably from above the critical temperature of the workingfluid to 250° C.

In a suitable embodiment, the temperature of operation at the expanderinlet can be any one of the following temperatures or within the range(inclusive) defined by any two numbers below:

-   -   about 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,        64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,        80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95,        96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108,        109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121,        122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134,        135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147,        148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160,        161, 162, and about 163, 164, 165, 166, 167, 168, 169, 170, 171,        172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184,        185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197,        198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210,        211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,        224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236,        237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249,        250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262,        263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275,        276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288,        289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301,        302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314,        315, 316, 317, 318, 319, 320, 321, 323, 323, 324, 325, 326, 327,        328, 329, 330, 331, 323, 333, 334, 335, 336, 337, 338, 339, 340,        341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353,        354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366,        367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379,        380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392,        393, 394, 395, 396, 397, 398, 399, 400° C.

The pressure of the working fluid in the expander is reduced from theexpander inlet pressure to the expander outlet pressure. Typicalexpander inlet pressures for super-critical cycles are within the rangeof from about 5 MPa to about 15 MPa, preferably from about 5 MPa toabout 10 MPa, and more preferably from about 5 MPa to about 8 MPa.Typical expander outlet pressures for super-critical cycles are within 1MPa above the critical pressure.

Typical expander inlet pressures for trans-critical cycles are withinthe range of from about the critical pressure to about 15 MPa,preferably from about the critical pressure to about 10 MPa, and morepreferably from about the critical pressure to about 8 MPa. Typicalexpander outlet pressures for trans-critical cycles are within the rangeof from about 0.15 MPa to about 1.8 MPa, more typically from about 0.25MPa to about 1.10 MPa, more typically from about 0.35 MPa to about 0.75MPa.

Typical expander inlet pressures for sub-critical cycles are within therange of from about 0.99 MPa to about 0.1 MPa below the criticalpressure, preferably from about 1.6 MPa to about 0.1 MPa below thecritical pressure, and more preferably from about 2.47 MPa to about 0.1MPa below the critical pressure. Typical expander outlet pressures forsub-critical cycles are within the range of from about 0.15 MPa to about1.8 MPa, more typically from about 0.25 MPa to about 1.10 MPa, moretypically from about 0.35 MPa to about 0.75 MPa.

The cost of a power cycle apparatus can increase when design for higherpressure is required. Accordingly, there is generally at least aninitial cost advantage to limiting the maximum cycle operating pressure.Of note are cycles where the maximum operating pressure (typicallypresent in the working fluid heater or evaporator and the expanderinlet) does not exceed 2.2 MPa.

The working fluids of the present invention may be used in an ORC systemto generate mechanical energy from heat extracted or received fromrelatively low temperature heat sources such as low pressure steam,industrial waste heat, solar energy, geothermal hot water, low-pressuregeothermal steam, or distributed power generation equipment utilizingfuel cells or turbines, including microturbines, or internal combustionengines.

One source of low-pressure steam could be the process known as a binarygeothermal Rankine cycle. Large quantities of low-pressure steam can befound in numerous locations, such as in fossil fuel powered electricalgenerating power plants.

Of note are sources of heat including waste heat recovered from gasesexhausted from mobile internal combustion engines (e.g. truck or ship orrail Diesel engines), waste heat from exhaust gases from stationaryinternal combustion engines (e.g. stationary Diesel engine powergenerators), waste heat from fuel cells, heat available at CombinedHeating, Cooling and Power or District Heating and Cooling plants, wasteheat from biomass fueled engines, heat from natural gas or methane gasburners or methane-fired boilers or methane fuel cells (e.g. atdistributed power generation facilities) operated with methane fromvarious sources including biogas, landfill gas and coal-bed methane,heat from combustion of bark and lignin at paper/pulp mills, heat fromincinerators, heat from low pressure steam at conventional steam powerplants (to drive “bottoming” Rankine cycles), and geothermal heat.

Also of note are sources of heat including solar heat from solar panelarrays including parabolic solar panel arrays, solar heat fromConcentrated Solar Power plants, heat removed from photovoltaic (PV)solar systems to cool the PV system to maintain a high PV systemefficiency.

Also of note are sources of heat including at least one operationassociated with at least one industry selected from the group consistingof: oil refineries, petrochemical plants, oil and gas pipelines,chemical industry, commercial buildings, hotels, shopping malls,supermarkets, bakeries, food processing industries, restaurants, paintcuring ovens, furniture making, plastics molders, cement kilns, lumberkilns, calcining operations, steel industry, glass industry, foundries,smelting, air-conditioning, refrigeration, and central heating.

In one embodiment of the Rankine cycles of this invention, geothermalheat is supplied to the working fluid circulating above ground (e.g.binary cycle geothermal power plants). In another embodiment of theRankine cycles of this invention, the working fluid is used both as theRankine cycle working fluid and as a geothermal heat carrier circulatingunderground in deep wells with the flow largely or exclusively driven bytemperature-induced fluid density variations, known as “the thermosyphoneffect”.

In other embodiments, the present invention also uses other types of ORCsystems, for example, small scale (e.g. 1-500 kw, preferably 5-250 kw)Rankine cycle systems using micro-turbines or small size positivedisplacement expanders, combined, multistage, and cascade RankineCycles, and Rankine Cycle systems with recuperators to recover heat fromthe vapor exiting the expander.

Other sources of heat include at least one operation associated with atleast one industry selected from the group consisting of: oilrefineries, petrochemical plants, oil and gas pipelines, chemicalindustry, commercial buildings, hotels, shopping malls, supermarkets,bakeries, food processing industries, restaurants, paint curing ovens,furniture making, plastics molders, cement kilns, lumber kilns,calcining operations, steel industry, glass industry, foundries,smelting, air-conditioning, refrigeration, and central heating.

Power Cycle Apparatus

In accordance with this invention, a power cycle apparatus forconverting heat to mechanical energy is provided. The apparatus containsa working fluid comprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze)and at least one compound selected from 1,1,2,2-tetrafluoroethane(HFC-134) and 1,1,1,2-tetrafluoroethane (HFC-134a). Typically, theapparatus of this invention includes a heat exchange unit where theworking fluid can be heated and an expander where mechanical energy canbe generated by expanding the heated working fluid by lowering itspressure. Expanders include turbo or dynamic expanders, such asturbines, and positive displacement expanders, such as screw expanders,scroll expanders, piston expanders and rotary vane expanders. Mechanicalpower can be used directly (e.g. to drive a compressor) or be convertedto electrical power through the use of electrical power generators.Typically the apparatus also includes a working fluid cooling unit(e.g., condenser or heat exchanger) for cooling the expanded workingfluid and a compressor for compressing the cooled working fluid.

In one embodiment, the power cycle apparatus of the present inventioncomprises (a) a heat exchange unit; (b) an expander in fluidcommunication with the heat exchange unit; (c) a working fluid coolingunit in fluid communication with the expander; and (d) a compressor influid communication with the working fluid cooler; wherein thecompressor is further being in fluid communication with the heatexchange unit such that the working fluid then repeats flow throughcomponents (a), (b), (c) and (d) in a repeating cycle; wherein theworking fluid comprises E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) andat least one compound selected from 1,1,2,2-tetrafluoroethane (HFC-134)and 1,1,1,2-tetrafluoroethane (HFC-134a).

In one embodiment, the power cycle apparatus uses a working fluidcomprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least onecompound selected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a). Of note are working fluids thatconsist essentially of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,2,2-tetrafluoroethane (HFC-134). Also of note are working fluidsthat consist essentially of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze),1,1,2,2-tetrafluoroethane (HFC-134), and 1,1,1,2-tetrafluoroethane(HFC-134a).

Of note for use in power cycle apparatus are compositions comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) that are non-flammable. Certaincompositions comprising E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) andat least one compound selected from 1,1,2,2-tetrafluoroethane (HFC-134)and 1,1,1,2-tetrafluoroethane (HFC-134a) are non-flammable by standardtest ASTM 681. It is expected that certain compositions comprisingE-HFO-1234ze and HFC-134 and/or HFC-134a are non-flammable by standardtest ASTM 681. Of particular note are compositions containingE-HFO-1234ze and HFC-134 and/or HFC-134a with no more than weightpercent 85 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with nomore than 84 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with nomore than 83 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with nomore than 82 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with nomore than 81 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with nomore than 80 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with atleast 78 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with atleast 76 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a with atleast 74 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a atleast 72 weight percent E-HFO-1234ze. Also of particular note arecompositions containing E-HFO-1234ze and HFC-134 and/or HFC-134a atleast 70 weight percent E-HFO-1234ze.

Of particular note, for use in power cycle apparatus, are compositionscontaining from about 35 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from about 5 to about 65 weight percentHFC-134.

Also of particular note, for use in power cycle apparatus, areazeotropic and azeotrope-like compositions containing from about 5 toabout 95 weight percent E-1,3,3,3-tetrafluoropropene and from about 5 toabout 95 weight percent HFC-134. Also of particular note, for use inpower cycle apparatus, are azeotropic and azeotrope-like compositionscontaining from about 5 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from about 40 to about 95 weightpercent HFC-134. Also of particular note, for use in power cycleapparatus, are azeotropic and azeotrope-like compositions containingfrom about 35 to about 60 weight percent E-1,3,3,3-tetrafluoropropeneand from about 40 to about 65 weight percent HFC-134.

Also of particular note, for use in power cycle apparatus, arecompositions containing from about 35 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from about 5 to about 65 weight percenttotal of HFC-134 and HFC-134a. Also of particular note, for use in powercycle apparatus, are azeotropic and azeotrope-like compositionscontaining from about 5 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from about 5 to about 95 weight percenttotal of HFC-134 and HFC-134a. Also of particular note, for use in powercycle apparatus, are azeotropic and azeotrope-like compositionscontaining from about 5 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from about 40 to about 95 weightpercent total of HFC-134 and HFC-134a. Also of particular note, for usein power cycle apparatus, are azeotropic and azeotrope-like compositionscontaining from about 35 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from about 40 to about 65 weightpercent total of HFC-134 and HFC-134a.

Also of particular utility in the power cycle apparatus are thoseembodiments wherein the working fluid has a low GWP. For GWP less than1000, compositions containing E-HFO-1234ze and HFC-134 comprise from 11weight percent to 99 weight percent E-HFO-1234ze and 89 weight percentto 1 weight percent HFC-134. For GWP less than 1000, compositionscontaining E-HFO-1234ze and HFC-134a comprise from 30.5 weight percentto 99 weight percent E-HFO-1234ze and 69.5 weight percent to 1 weightpercent HFC-134a.

For GWP less than 500, compositions containing E-HFO-1234ze and HFC-134comprise from 56 weight percent to 99 weight percent E-HFO-1234ze and 44weight percent to 1 weight percent HFC-134. For GWP less than 500,compositions containing E-HFO-1234ze and HFC-134a comprise from 65.5weight percent to 99 weight percent E-HFO-1234ze and 34.5 weight percentto 1 weight percent HFC-134a.

For GWP less than 150, compositions containing E-HFO-1234ze and HFC-134comprise from 87.5 weight percent to 99 weight percent E-HFO-1234ze and12.5 weight percent to 1 weight percent HFC-134. For GWP less than 150,compositions containing E-HFO-1234ze and HFC-134a comprise from 90weight percent to 99 weight percent E-HFO-1234ze and 10 weight percentto 1 weight percent HFC-134a.

FIG. 1 shows a schematic of one embodiment of the ORC system for usingheat from a heat source. Heat supply heat exchanger 40 transfers heatsupplied from heat source 46 to the working fluid entering heat supplyheat exchanger 40 in liquid phase. Heat supply heat exchanger 40 is inthermal communication with the source of heat (the communication may beby direct contact or another means). In other words, heat supply heatexchanger 40 receives heat energy from heat source 46 by any known meansof thermal transfer. The ORC system working fluid circulates throughheat supply heat exchanger 40 where it gains heat. At least a portion ofthe liquid working fluid converts to vapor in heat supply heat exchanger(e.g. evaporator) 40.

The working fluid now in vapor form is routed to expander 32 where theexpansion process results in conversion of at least a portion of theheat energy supplied from the heat source into mechanical shaft power.The shaft power can be used to do any mechanical work by employingconventional arrangements of belts, pulleys, gears, transmissions orsimilar devices depending on the desired speed and torque required. Inone embodiment, the shaft can also be connected to electricpower-generating device 30 such as an induction generator. Theelectricity produced can be used locally or delivered to a grid.

The working fluid still in vapor form that exits expander 32 continuesto condenser 34 where adequate heat rejection causes the fluid tocondense to liquid.

It is also desirable to have liquid surge tank 36 located betweencondenser 34 and pump 38 to ensure there is always an adequate supply ofworking fluid in liquid form to the pump suction. The working fluid inliquid form flows to pump 38 that elevates the pressure of the fluid sothat it can be introduced back into heat supply heat exchanger 40 thuscompleting the Rankine cycle loop.

In an alternative embodiment, a secondary heat exchange loop operatingbetween the heat source and the ORC system can also be used. In FIG. 2,an organic Rankine cycle system is shown, in particular for a systemusing a secondary heat exchange loop. The main organic Rankine cycleoperates as described above for FIG. 1. The secondary heat exchange loopis shown in FIG. 2 as follows: the heat from heat source 46′ istransported to heat supply heat exchanger 40′ using a heat transfermedium (i.e., secondary heat exchange loop fluid). The heat transfermedium flows from heat supply heat exchanger 40′ to pump 42′ that pumpsthe heat transfer medium back to heat source 46′. This arrangementoffers another means of removing heat from the heat source anddelivering it to the ORC system.

In fact, the working fluids of this invention can be used as secondaryheat exchange loop fluids provided the pressure in the loop ismaintained at or above the fluid saturation pressure at the temperatureof the fluid in the loop. Alternatively, the working fluids of thisinvention can be used as secondary heat exchange loop fluids or heatcarrier fluids to extract heat from heat sources in a mode of operationin which the working fluids are allowed to evaporate during the heatexchange process thereby generating large fluid density differencessufficient to sustain fluid flow (thermosyphon effect). Additionally,high-boiling point fluids such as glycols, brines, silicones, or otheressentially non-volatile fluids may be used for sensible heat transferin the secondary loop arrangement described. A secondary heat exchangeloop can make servicing of either the heat source or the ORC systemeasier since the two systems can be more easily isolated or separated.This approach can simplify the heat exchanger design as compared to thecase of having a heat exchanger with a high mass flow/low heat fluxportion followed by a high heat flux/low mass flow portion.

Organic compounds often have an upper temperature limit above whichthermal decomposition will occur. The onset of thermal decompositionrelates to the particular structure of the chemical and thus varies fordifferent compounds. In order to access a high-temperature source usingdirect heat exchange with the working fluid, design considerations forheat flux and mass flow, as mentioned above, can be employed tofacilitate heat exchange while maintaining the working fluid below itsthermal decomposition onset temperature. Direct heat exchange in such asituation typically requires additional engineering and mechanicalfeatures which drive up cost. In such situations, a secondary loopdesign may facilitate access to the high-temperature heat source bymanaging temperatures while circumventing the concerns enumerated forthe direct heat exchange case.

Other ORC system components for the secondary heat exchange loopembodiment are essentially the same as described for FIG. 1. In FIG. 2,Liquid pump 42′ circulates the secondary fluid (e.g., heat transfermedium) through the secondary loop so that it enters the portion of theloop in heat source 46′ where it gains heat. The fluid then passes toheat exchanger 40′ where the secondary fluid gives up heat to the ORCworking fluid.

In one embodiment of the above process, the evaporator temperature(temperature at which heat is extracted by the working fluid) is lessthan the critical temperature of the working fluid. Included areembodiments wherein the temperature of operation is any one of thefollowing temperatures or within the range (inclusive) defined by anytwo numbers below:

-   -   about 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,        54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69,        70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85,        86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100,        101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113,        114, 115, 116, 117, 118, and about 119° C.

In one embodiment of the above process, the evaporator operatingpressure is less than about 2.2 MPa. Included are embodiments whereinthe pressures of operation is any one of the following pressures orwithin the range (inclusive) defined by any two numbers below:

-   -   about 0.15, 0.2, 0. 25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6,        0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.00, 1.05, 1.10, 1.15,        1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65,        1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15,        2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65,        2.70, 2.75, 2.80, 2.85, 2.90, 2.95, 3.00, 3.05, 3.10, 3.15,        3.20, 3.25, 3.30, 3.35, 3.40, 3.45, 3.50, 3.55, 3.60, 3.65,        3.70, 3.75, 3.80, 3.85, 3.90, 3.95, 4.00, 4.05, 4.10, 4.15,        4.20, 4.25, 4.30, 4.35, 4.40, 4.45, 4.50, 4.55, and about 4.60        MPa.

The use of low cost equipment components substantially expands thepractical viability of organic Rankine cycles. For example, limiting themaximum evaporating pressure to about 2.2 MPa would allow the use oflow-cost equipment components of the type widely used in the HVACindustry.

Of particular note are power cycle apparatus containing a working fluidcomprising or consisting essentially of E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze) and at least one compound selected from1,1,2,2-tetrafluoroethane (HFC-134) and 1,1,1,2-tetrafluoroethane(HFC-134a).

Also of particular note are power cycle apparatus containing a workingfluid comprising or consisting essentially ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,2,2-tetrafluoroethane (HFC-134).

Also of particular note are power cycle apparatus containing a workingfluid comprising or consisting essentially ofE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze), 1,1,2,2-tetrafluoroethane(HFC-134), and 1,1,1,2-tetrafluoroethane (HFC-134a).

Of particular utility are non-flammable working fluids comprisingmixtures of E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least onecompound selected from 1,1,2,2-tetrafluoroethane (HFC-134) and1,1,1,2-tetrafluoroethane (HFC-134a) with GWP less than 150. Also ofparticular utility are non-flammable working fluids comprising mixturesof E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and1,1,2,2-tetrafluoroethane (HFC-134) with GWP less than 150. Also ofparticular utility are non-flammable working fluids comprising mixturesof E-1,3,3,3-tetrafluoropropene (E-HFO-1234ze),1,1,2,2-tetrafluoroethane (HFC-134), and 1,1,1,2-tetrafluoroethane(HFC-134a) with GWP less than 150.

The apparatus may include molecular sieves to aid in removal ofmoisture. Desiccants may be composed of activated alumina, silica gel,or zeolite-based molecular sieves. In some embodiments, the molecularsieves are most useful with a pore size of approximately 3 Angstroms, 4Angstroms, or 5 Angstroms. Representative molecular sieves includeMOLSIV XH-7, XH-6, XH-9 and XH-11 (UOP LLC, Des Plaines, Ill.).

Power Cycle Compositions

In some embodiments, the compositions comprisingE-1,3,3,3-tetrafluoropropene (E-HFO-1234ze) and at least one compoundselected from 1, 1,2,2-tetrafluoroethane (HFC-134) and 1, 1,1,2-tetrafluoroethane (HFC-134a) that are particularly useful in powercycles including organic Rankine cycles are azeotropic orazeotrope-like.

It has been disclosed that E-1,3,3,3-tetrafluoropropene and HFC-134 aswell as E-1,3,3,3-tetrafluoropropene and HFC-134a form azeotropic andazeotrope-like compositions in U.S. Published Patent Application20060243944(A1).

Azeotropic compositions will have zero glide in the heat exchangers,e.g., evaporator and condenser (or working fluid cooler), of a powercycle apparatus.

In accordance with this invention, a working fluid comprising anazeotropic or azeotrope-like combination of E-1,3,3,3-tetrafluoropropene(E-HFO-1234ze), 1,1,2,2-tetrafluoroethane (HFC-134), and1,1,1,2-tetrafluoroethane (HFC-134a) is provided. The azeotropic orazeotrope-like combination comprises from about 1 weight percent toabout 98 weight percent E-HFO-1234ze, from about 1 weight percent toabout 98 weight percent HFC-134 and from about 1 weight percent to about98 weight percent HFC-134a.

In one embodiment is provided a composition suitable for use in organicRankine apparatus, comprising a working fluid containing E-HFO-1234ze,HFC-134a, and HFC-134 and a lubricant.

In one embodiment, any of the compositions disclosed herein may be usedin combination with at least one lubricant selected from the groupconsisting of polyalkylene glycols, polyol esters, polyvinylethers,polycarbonates, perfluoropolyethers, mineral oils, alkylbenzenes,synthetic paraffins, synthetic naphthenes, poly(alpha)olefins andcombinations thereof.

In some embodiments, lubricants useful in combination with thecompositions as disclosed herein may comprise those suitable for usewith power cycle apparatus, including organic Rankine cycle apparatus.Among these lubricants are those conventionally used in vaporcompression refrigeration apparatus utilizing chlorofluorocarbonrefrigerants. In one embodiment, lubricants comprise those commonlyknown as “mineral oils” in the field of compression refrigerationlubrication. Mineral oils comprise paraffins (i.e., straight-chain andbranched-carbon-chain, saturated hydrocarbons), naphthenes (i.e. cyclicparaffins) and aromatics (i.e. unsaturated, cyclic hydrocarbonscontaining one or more rings characterized by alternating double bonds).In one embodiment, lubricants comprise those commonly known as“synthetic oils” in the field of compression refrigeration lubrication.Synthetic oils comprise alkylaryls (i.e. linear and branched alkylalkylbenzenes), synthetic paraffins and naphthenes, andpoly(alphaolefins). Representative conventional lubricants are thecommercially available BVM 100 N (paraffinic mineral oil sold by BVAOils), naphthenic mineral oil commercially available from Crompton Co.under the trademarks Suniso® 3GS and Suniso® 5GS, naphthenic mineral oilcommercially available from Pennzoil under the trademark Sontex® 372LT,naphthenic mineral oil commercially available from Calumet Lubricantsunder the trademark Calumet® RO-30, linear alkylbenzenes commerciallyavailable from Shrieve Chemicals under the trademarks Zerol® 75, Zerol®150 and Zerol® 500, and HAB 22 (branched alkylbenzene sold by NipponOil). Perfluoropolyether (PFPE) lubricants include those sold under thetrademark Krytox® by E. I. du Pont de Nemours; sold under the trademarkFomblin® by Ausimont; or sold under the trademark Demnum® by DaikinIndustries.

In other embodiments, lubricants may also comprise those which have beendesigned for use with hydrofluorocarbon refrigerants and are misciblewith refrigerants of the present invention under compressionrefrigeration and air-conditioning apparatus' operating conditions. Suchlubricants include, but are not limited to, polyol esters (POEs) such asCastrol® 100 (Castrol, United Kingdom), polyalkylene glycols (PAGs) suchas RL-488A from Dow (Dow Chemical, Midland, Michigan), polyvinyl ethers(PVEs), and polycarbonates (PCs).

In another embodiment is provided composition suitable for use inorganic Rankine apparatus, comprising a working fluid containingE-HFO-1234ze, HFC-134 and HFC-134a and at least one other componentselected from the group consisting of stabilizers, compatibilizers andtracers.

Optionally, in another embodiment, certain refrigeration,air-conditioning, or heat pump system additives may be added, asdesired, to the working fluids as disclosed herein in order to enhanceperformance and system stability. These additives are known in the fieldof refrigeration and air-conditioning, and include, but are not limitedto, anti-wear agents, extreme pressure lubricants, corrosion andoxidation inhibitors, metal surface deactivators, free radicalscavengers, and foam control agents. In general, these additives may bepresent in the working fluids in small amounts relative to the overallcomposition. Typically concentrations of from less than about 0.1 weightpercent to as much as about 3 weight percent of each additive are used.These additives are selected on the basis of the individual systemrequirements. These additives include members of the triaryl phosphatefamily of EP (extreme pressure) lubricity additives, such as butylatedtriphenyl phosphates (BTPP), or other alkylated triaryl phosphateesters, e.g. Syn-0-Ad 8478 from Akzo Chemicals, tricresyl phosphates andrelated compounds. Additionally, the metal dialkyl dithiophosphates(e.g., zinc dialkyl dithiophosphate (or ZDDP); Lubrizol 1375 and othermembers of this family of chemicals may be used in compositions of thepresent invention. Other antiwear additives include natural product oilsand asymmetrical polyhydroxyl lubrication additives, such as SynergolTMS (International Lubricants). Similarly, stabilizers such asantioxidants, free radical scavengers, and water scavengers may beemployed. Compounds in this category can include, but are not limitedto, butylated hydroxy toluene (BHT), epoxides, and mixtures thereof.Corrosion inhibitors include dodecyl succinic acid (DDSA), aminephosphate (AP), oleoyl sarcosine, imidazone derivatives and substitutedsulfphonates. Metal surface deactivators include areoxalylbis(benzylidene) hydrazide,N,N′-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoylhydrazine, 2,2,' -oxamidobis-ethyl-(3,5-di-tert-butyl-4-hydroxyhydrocinnamate,N,N′-(disalicyclidene)-1,2-diaminopropane andethylenediaminetetra-acetic acid and its salts, and mixtures thereof.

Of note are stabilizers to prevent degradation at temperatures of 50° C.or above. Also of note are stabilizers to prevent degradation attemperatures of 75° C. or above. Also of note are stabilizers to preventdegradation at temperatures of 85° C. or above. Also of note arestabilizers to prevent degradation at temperatures of 100° C. or above.Also of note are stabilizers to prevent degradation at temperatures of118° C. or above. Also of note are stabilizers to prevent degradation attemperatures of 137° C. or above.

Of note are stabilizers comprising at least one compound selected fromthe group consisting of hindered phenols, thiophosphates, butylatedtriphenylphosphorothionates, organo phosphates, or phosphites, arylalkyl ethers, terpenes, terpenoids, epoxides, fluorinated epoxides,oxetanes, ascorbic acid, thiols, lactones, thioethers, amines,nitromethane, alkylsilanes, benzophenone derivatives, aryl sulfides,divinyl terephthalic acid, diphenyl terephthalic acid, ionic liquids,and mixtures thereof. Representative stabilizer compounds include butare not limited to tocopherol; hydroquinone; t-butyl hydroquinone;monothiophosphates; and dithiophosphates, commercially available fromCiba Specialty Chemicals, Basel, Switzerland, hereinafter “Ciba,” underthe trademark Irgalube® 63; dialkylthiophosphate esters, commerciallyavailable from Ciba under the trademarks Irgalube® 353 and Irgalube®350, respectively; butylated triphenylphosphorothionates, commerciallyavailable from Ciba under the trademark Irgalube® 232; amine phosphates,commercially available from Ciba under the trademark Irgalube® 349(Ciba); hindered phosphites, commercially available from Ciba asIrgafos® 168; a phosphate such as (Tris-(di-tert-butylphenyl),commercially available from Ciba under the trademark Irgafos® OPH;(Di-n-octyl phosphite); and iso-decyl diphenyl phosphite, commerciallyavailable from Ciba under the trademark Irgafos® DDPP; anisole;1,4-dimethoxybenzene; 1,4-diethoxybenzene; 1,3,5-trimethoxybenzene;d-limonene; retinal; pinene; menthol; Vitamin A; terpinene; dipentene;lycopene; beta carotene; bornane; 1,2-propylene oxide; 1,2-butyleneoxide; n-butyl glycidyl ether; trifluoromethyloxirane;1,1-bis(trifluoromethyl)oxirane; 3-ethyl-3-hydroxymethyl-oxetane, suchas OXT-101 (Toagosei Co., Ltd); 3-ethyl-3-((phenoxy)methyl)-oxetane,such as OXT-211 (Toagosei Co., Ltd);3-ethyl-34(2-ethyl-hexyloxy)methyl)-oxetane, such as OXT-212 (ToagoseiCo., Ltd); ascorbic acid; methanethiol (methyl mercaptan); ethanethiol(ethyl mercaptan); Coenzyme A; dimercaptosuccinic acid (DMSA);grapefruit mercaptan ((R)-2-(4-methylcyclohex-3-enyl)propane-2-thiol));cysteine ((R)-2-amino-3-sulfanyl-propanoic acid); lipoamide(1,2-dithiolane-3-pentanamide); 5,7-bis(1,1-dimethylethyl)-3-[2,3(or3,4)-dimethylphenyl]-2(3H)-benzofuranone, commercially available fromCiba under the trademark Irganox® HP-136; benzyl phenyl sulfide;diphenyl sulfide; diisopropylamine; dioctadecyl 3,3′-thiodipropionate,commercially available from Ciba under the trademark Irganox® PS 802(Ciba); didodecyl 3,3′-thiopropionate, commercially available from Cibaunder the trademark Irganox® PS 800;di-(2,2,6,6-tetramethyl-4-piperidyl)sebacate, commercially availablefrom Ciba under the trademark Tinuvin® 770;poly-(N-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidyl succinate,commercially available from Ciba under the trademark Tinuvin® 622LD(Ciba); methyl bis tallow amine; bis tallow amine;phenol-alpha-naphthylamine; bis(dimethylamino)methylsilane (DMAMS);tris(trimethylsilyl)silane (TTMSS); vinyltriethoxysilane;vinyltrimethoxysilane; 2,5-difluorobenzophenone;2′,5′-dihydroxyacetophenone; 2-aminobenzophenone; 2-chlorobenzophenone;benzyl phenyl sulfide; diphenyl sulfide; dibenzyl sulfide; ionicliquids; and others.

Tracers that may be included in the working fluid compositions may beselected from the group consisting of hydrofluorocarbons (HFCs),deuterated hydrofluorocarbons, perfluorocarbons, fluoroethers,brominated compounds, iodated compounds, alcohols, aldehydes andketones, nitrous oxide and combinations thereof.

The compositions of the present invention can be prepared by anyconvenient method including mixing or combining the desired amounts. Inone embodiment of this invention, a composition can be prepared byweighing the desired component amounts and thereafter combining them inan appropriate container.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

Example 1 Power Generation through Subcritical Rankine Cycle Using anE-HFO-1234ze/HFC-134 Blend as the Working Fluid

Heat at temperatures up to about 100° C. is abundantly available fromvarious sources. It can be captured as a byproduct from variousindustrial processes, it can be collected from solar irradiation throughsolar panels or it can be extracted from geological hot water reservoirsthrough shallow or deep wells. Such heat can be converted to mechanicalor electrical power for various uses through Rankine cycles usingE-HFO-1234ze/HFC-134 (or E-HFO-1234ze/HFC-134/HFC-134a) blends as theworking fluid.

Table 1 compares the basic properties of an E-HFO-1234ze/HFC-134 blendcontaining 65 wt% E-HFO-1234ze (Blend A) to those of HFC-134a. HFC-134awas selected as a reference fluid because it has been extensively usedas a working fluid for Rankine cycles using heat at temperatures up toabout 100° C. Blend A retains the attractive safety properties ofHFC-134a, i.e. low toxicity and non-flammability. Moreover, Blend A hasa GWP₁₀₀ lower than that of HFC-134a by 72.8%

TABLE 1 Basic properties of an E-HFO-1234ze/HFC-134 blend containing 65wt % E-HFO-1234ze compared to those of HFC-134a. HFC-134a Blend AChemical Identity CH₂FCF₃ E-HFO-1234ze/HFC-134 [65/35 wt %] ToxicityClass A A(*) (ASHRAE Standard 34) Flammability Class 1 1(*) (ASHRAEStandard 34) (non- (non-flammable) flammable) ODP None None GWP₁₀₀ 1,430389 T_(cr) [° C.] 101.1 111.6 P_(cr) [MPa] 4.06 3.96 T_(b) [° C.] −26.1−20.5 Glide [° C.] N/A Negligible (*)estimated

Table 2 compares the performance of Rankine cycles operating with BlendA to Rankine Cycles operating with HFC-134a. All cycles are assumed tobe operating at the following conditions:

T_(cond) [C.] 35 Superh [C.] 10 Subc [C.] 5 Expander Efficiency 0.8Liquid Pump Efficiency 0.7

TABLE 2 Performance of Rankine cycles operating with Blend A to RankineCycles operating with HFC-134a Column No. 3 6 1 Blend A 4 Blend A HFC- 2vs HFC- 5 vs 7 134a Blend A HFC-134a % 134a Blend A HFC-134a % Blend AT_(evap) [C.] 80 80 90 90 100 Evaporator N/A 0.08 N/A 0.08 0.06 Glide [°C.] Condenser N/A 0.08 N/A 0.08 0.08 Glide [° C.] P_(evap) [MPa] 2.642.12 3.25 2.61 3.19 Net Work from 15.98 16.34 18.01 18.81 20.73 Cycle[kJ/kg] Cycle Energy 7.79 7.97 2.31 8.78 9.07 3.30 9.95 Efficiency [%]

Columns 1, 2 and 3 of Table 2 indicate that Blend A, could enableRankine cycles for the utilization of heat at temperatures that wouldallow an evaporating temperature of 80° C. (and an expander inlettemperature of 90° C.) with energy efficiency 2.31% higher thanHFC-134a. The lower evaporating temperature with Blend A would also beadvantageous. FIG. 3 shows that the vapor pressure of Blend A attemperatures higher than about 80° C. is substantially lower than thatof HFC-134a.

Columns 4, 5 and 6 of Table 2 indicate that Blend A, could enableRankine cycles for the utilization of heat at temperatures that wouldallow an evaporating temperature of 90° C. (and an expander inlettemperature of 100° C.) with energy efficiency 3.30% higher thanHFC-134a.

The higher critical temperature of Blend A relative to HFC-134a allowsthe use of heat in conventional subcritical Rankine cycles attemperatures higher than those feasible with HFC-134a. Column 7 of Table2 shows the performance of a Rankine cycle operating with Blend A as theworking fluid for the utilization of heat at temperatures that wouldallow an evaporating temperature of 100° C. (and an expander inlettemperature of 110° C.). Use of HFC-134a in a conventional subcriticalRankine cycle would not be practical at an evaporating temperature of100° C. because of the close proximity of the evaporating temperature tothe critical temperature of HFC-134a. The cycle energy efficiency withBlend A (9.95%) is 13.33% higher than the highest energy efficiency thatcan be achieved with HFC-134a (8.78%, Table 2, column 4) withconventional subcritical Rankine cycles operating at evaporatingtemperatures lower than the critical temperatures of their workingfluids by at least about 10° C. (or at reduced evaporating temperatureslower than about 0.97). In summary, replacing HFC-134a with blend Awould allow higher energy efficiencies especially when the availableheat source allows the evaporating temperature to be increased, inaddition to reducing the GWP of the working fluid.

Example 2 Chemical Stability of E-HFO-1234ze and HFC-134 at 250° C.

The chemical stability of E-HFO-1234ze in the presence of metals wastested according to the sealed tube testing methodology of ANSI/ASHRAE

Standard 97-2007. The stock of E-HFO-1234ze used in the sealed tubetests was about 99.98 wt% pure and contained virtually no water or air.

Sealed glass tubes, each containing three metal coupons made of steel,copper, and aluminum immersed in E-HFO-1234ze, were aged in a heatedoven at 250° C. for 7 or 14 days. Visual inspection of the tubes afterthermal aging indicated clear liquids with no discoloration or othervisible deterioration of the fluid. Moreover, there was no change in theappearance of the metal coupons indicating corrosion or otherdegradation. The concentration of fluoride ion in the aged liquidsamples, measured by ion chromatography, was 15.15 ppm after two weeksof aging at 250° C. The concentration of fluoride ion can be interpretedas an indicator of the degree of E-HFO-1234ze degradation. Therefore,E-HFO-1234ze degradation was minimal.

Table 3 shows compositional changes of E-HFO-1234ze samples after agingin the presence of steel, copper and aluminum at 250° C. for one or twoweeks. The conversion of E-HFO-1234ze even after two weeks of aging wasminimal. Isomerization of E-HFO-1234ze produced 963.2 ppm of the cis orE isomer of HFO-1234ze. Although the thermodynamic properties ofHFO-1234ze-Z are significantly different than those of E-HFO-1234ze, thethermodynamic properties of an E-HFO-1234ze/HFO-1234ze-Z blendcontaining only 963.2 ppm of HFO-1234ze-Z would be virtually identicalto the thermodynamic properties of pure E-HFO-1234ze.

Only negligible proportions of new unknown compounds appeared even aftertwo weeks of aging at 250° C.

TABLE 3 Changes in E-HFO-1234ze sample composition (quantified by GCMSpeak areas) after aging in the presence of steel, copper and aluminumcoupons at 250° C. for one and two weeks. Initial (Non-Aged) After oneAfter two Stock of week of weeks of E-HFO-1234ze aging agingE-HFO-1234ze [%] 99.97684 99.92775 99.83044 Z-HFO-1234ze [ppm] 1.0 196.1963.2 HFO-1234 [ppm] 4.5 131.4 188.4 Unknown compounds [ppm] <1 154 295eluting after E-HFO- 1234ze

The chemical stability of HFC-134 was also tested following proceduressimilar to those described above for E-HFO-1234ze. The fluoride ionconcentration in HFC-134 samples aged in the presence of steel, copper,and aluminum at 250° C. for two weeks was below the measurement methoddetection limit (0.15 ppm), indicating a high level of stability at thistemperature.

Example 3 Power Generation through Transcritical Rankine Cycle Using anE-HFO-1234ze/HFC-134 Blend as the Working Fluid

This example demonstrates the generation of power from heat throughRankine Cycles using working fluids containing E-HFO-1234ze and HFC-134under transcritical cycle conditions. The evidence provided in example 2above strongly suggests that E-HFO-1234ze and HFC-134 blends can remainchemically stable at temperatures substantially higher than theircritical temperatures. Therefore, working fluids comprising E-HFO-1234zeand HFC-134 can enable Rankine cycles that collect heat at temperaturesand pressures at which the working fluids containing HFO-1234ze andHFC-134 can be in a supercritical state. Use of higher temperature heatsources can lead to higher cycle energy efficiencies (and volumetriccapacities for power generation) relative to the use of lowertemperature heat sources.

When a supercritical fluid heater is used instead of the evaporator (orboiler) of the conventional subcritical Rankine cycle, the heaterpressure and the heater exit temperature (or equivalently the expanderinlet temperature) must be specified. Table 4 summarizes the performanceof a Rankine cycle with a blend containing 65 wt % E-HFO-1234ze and 35wt % HFC-134 as the working fluid. Operating the supercritical fluidheater at a pressure of 8 MPa and a heater exit temperature (or expanderinlet temperature) of 250° C. achieves a Rankine cycle energy efficiencyof 14.9%. Higher operating pressures in the supercritical fluid heaterwould necessitate the use of more robust equipment.

TABLE 4 Performance of a trans-critical Rankine Cycle with a 65/35 wt %E-HFO- 1234ze/HFC-134 blend as the working fluid Supercritical FluidHeater Pressure 8 MPa Expander Inlet Temperature 250.00° C. CondenserTemperature 35.00° C. Subcooling 5.00 K Expander Efficiency 0.80 LiquidPump Efficiency 0.70 Expander Outlet Temperature 159.98° C. ExpanderOutlet Pressure 0.71 MPa Net Work from Rankine Cycle 52.09 kJ/kgEfficiency Rankine Cycle 14.9% Volumetric Capacity for Power 1,167.83kJ/m³ Generation

Example 4 Impact of Vapor Leakage

A vessel is charged with an initial composition at a temperature ofabout 25° C., and the initial vapor pressure of the composition ismeasured. The composition is allowed to leak from the vessel, while thetemperature is held constant, until 50 weight percent of the initialcomposition is removed, at which time the vapor pressure of thecomposition remaining in the vessel is measured. Data are shown in Table5.

TABLE 5 After After 50% 50% Composition Initial P Initial P Leak LeakDelta P wt % (Psia) (kPa) (Psia) (kPa) (%) HFC-134/HFC-134a/E-HFO-1234ze 1/1/98 72.68 72.57 0.2%  1/98/1 96.10 96.07 0.0% 98/1/1 76.47 76.420.1% 10/10/80 77.24 76.54 0.9% 10/80/10 93.22 92.92 0.3% 80/10/10 79.3178.98 0.4% 20/20/60 81.15 80.39 0.9% 20/60/20 89.79 89.26 0.6% 60/20/2081.95 81.49 0.6% 25/25/50 82.71 82.01 0.8% 25/50/25 87.97 87.37 0.7%50/25/25 83.09 82.59 0.6% 30/30/40 84.03 83.39 0.8% 30/40/30 86.08 85.460.7% 40/30/30 84.14 83.58 0.7% 15/15/70 79.33 78.56 1.0% 15/70/15 91.5391.11 0.5% 70/15/15 80.69 80.28 0.5%

The data for compositions containing E-HFO-1234ze, HFC-134 and HFC-134aas listed in Table 5 demonstrates azeotrope-like behavior whereinremaining after 50 weight percent is removed the change in vaporpressure is less than about 10 percent.

Example 5 Performance of an Organic Rankine Cycle with the non-flammableHFO-1234ze-E/HFC-134 (63/37wt %) Blend as the Working Fluid Relative toNeat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASHRAE Standard 34) HFO-1234ze-E/HFC-134(63/37wt %) blend as the working fluid relative to neat HFO-1234ze-E:

TABLE 6 Blend B vs. E-HFO- HFO- 1234ze 1234ze-E Blend B (%) E-HFO-1234ze(wt %) 100 63 HFC-134 (wt %) 0 37 GWP₁₀₀ (AR4) 6 411 EvaporatorTemperature 90 90 (C.) Condenser Temperature 20 20 (C.) Pump Efficiency0.65 0.65 Turbine Efficiency 0.75 0.75 Superheat (K) 5 5 Subcooling (K)0 0 Pressure, evaporator (MPa) 2.47 2.62 Pressure, condenser (MPa) 0.430.45 Pump Work (kJ/kg) 2.95 3.01 2.0 Expander Work (kJ/kg) 25.08 26.094.0 Net Work 22.13 23.08 4.3 Thermal Efficiency 0.107 0.108 0.7Volumetric Capacity (kJ/m³) 461.7 494.5 7.1 Evaporator Glide (K) 0.07Condenser Glide (K) 0.07

Blend B offers non-flammability (according to ASHRAE Standard 34) andbetter performance than HFO-1234ze-E (higher efficiency and volumetriccapacity) while still achieving a relatively low GWP.

Example 6 Performance of an Organic Rankine Cycle with the non-flammableHFO-1234ze-E/HFC-134 (35/65wt %) Blend as the Working Fluid Relative toNeat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASHRAE Standard 34) HFO-1234ze-E/HFC-134(35/65wt %) blend as the working fluid relative to neat HFO-1234ze-E:

TABLE 7 HFO- Blend C vs. HFO- 1234ze-E Blend C 1234ze-E (%) E-HFO-1234ze(wt %) 100 35 HFC-134 (wt %) 0 65 GWP₁₀₀ (AR4) 6 717 EvaporatorTemperature (C.) 90 90 Condenser Temperature (C.) 20 20 Pump Efficiency0.65 0.65 Turbine Efficiency 0.75 0.75 Superheat (K) 5 5 Subcooling (K)0 0 Pressure, evaporator (MPa) 2.47 2.68 Pressure, condenser (MPa) 0.430.46 Pump Work (kJ/kg) 0.01 Expander Work (kJ/kg) 0 Net Work 2.95 2.970.8 Thermal Efficiency 25.08 27.20 8.5 Volumetric Capacity (kJ/m³) 22.1324.23 9.5 Evaporator Glide (K) 0.107 0.109 1.9 Condenser Glide (K) 461.7509.7 10.4

Blend C offers non flammability (according to ASHRAE Standard 34) andbetter performance than HFO-1234ze-E (higher efficiency and volumetriccapacity) while still achieving a relatively low GWP (relative to manyincumbent working fluids).

Example 7 Performance of an Organic Rankine Cycle with theHFO-1234ze-E/HFC-134 (95/5wt %) Blend as the Working Fluid Relative toNeat HFO-1234ze-E

The following table compares the performance of an ORC with theHFO-1234ze-E/HFC-134 (95/5wt %) blend as the working fluid relative toneat HFO-1234ze-E:

TABLE 8 HFO- Blend D vs. 1234ze-E Blend D HFO-1234ze-E E-HFO-1234ze (wt%) 100 95 HFC-134 (wt %) 0 5 GWP₁₀₀ (AR4) 6 61 Evaporator Temperature(C.) 90 90 Condenser Temperature (C.) 20 20 Pump Efficiency 0.65 0.65Turbine Efficiency 0.75 0.75 Superheat (K) 5 5 Subcooling (K) 0 0Pressure, evaporator (MPa) 2.47 2.49 Pressure, condenser (MPa) 0.43 0.43Pump Work (kJ/kg) 2.95 2.97 0.5 Expander Work (kJ/kg) 25.08 25.19 0.4Net Work 22.13 22.22 0.4 Thermal Efficiency 0.107 0.107 0.0 VolumetricCapacity (kJ/m³) 461.7 466.9 1.1 Evaporator Glide (K) 0.04 CondenserGlide (K) 0.06

Blend D offers higher volumetric capacity than 1234ze-E while stillachieving a low GWP relatively to many incumbent working fluids.

Example 8 Performance of an Organic Rankine Cycle with the Non-FlammableHFO-1234ze-E/HFC-134a (55/45wt %) Blend as the Working Fluid Relative toNeat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASHRAE Standard 34) HFO-1234ze-E/HFC-134a(55/45wt %) blend as the working fluid relative to neat E-HFO-1234ze:

TABLE 9 HFO- Blend E vs. 1234ze-E Blend E HFO-1234ze-E E-HFO-1234ze (wt%) 100 55 HFC-134a (wt %) 0 45 GWP₁₀₀ (AR4) 6 646.8 EvaporatorTemperature (C.) 90 90 Condenser Temperature (C.) 20 20 Pump Efficiency0.65 0.65 Turbine Efficiency 0.75 0.75 Superheat (K) 5 5 Subcooling (K)0 0 Pressure, evaporator (MPa) 2.47 2.87 Pressure, condenser (MPa) 0.430.51 Pump Work (kJ/kg) 2.95 3.43 16.3 Expander Work (kJ/kg) 25.08 25.080.0 Net Work 22.13 21.65 −2.2 Thermal Efficiency 0.107 0.105 −2.2Volumetric Capacity (kJ/m³) 461.7 524.9 13.7 Evaporator Glide (K) 0.41Condenser Glide (K) 0.65

Blend E offers higher volumetric capacity than 1234ze-E while stillachieving a low GWP relatively to many incumbent working fluids.

Example 9 Performance of an Organic Rankine Cycle with the Non-FlammableHFO-1234ze-E/HFC-134a (70/30 wt %) Blend as the Working Fluid Relativeto Neat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASTM E-681 at 60° C.) HFO-1234ze-E/HFC-134a(70/30 wt %) blend as the working fluid relative to neat HFO-1234ze-E:

TABLE 10 HFO- Blend F vs. 1234ze-E Blend F HFO-1234ze-E (%) E-HFO-1234ze(wt %) 100 70 HFC-134a (wt %) 0 30 GWP₁₀₀ (AR4) 6 433.2 CriticalTemperature (C.) 110.2 Critical Pressure (MPa) 3.66 EvaporatorTemperature (C.) 90 Condenser Temperature (C.) 20 Pump Efficiency 0.65Turbine Efficiency 0.75 Superheat (K) 5 Subcooling (K) 0 Pressure,evaporator (MPa) 2.47 2.75 Pressure, condenser (MPa) 0.43 0.48 Pump Work(kJ/kg) 2.95 3.28 11.2 Expander Work (kJ/kg) 25.08 25.05 −0.1 Net Work22.13 21.77 −1.7 Thermal Efficiency 0.107 0.105 −1.6 Volumetric Capacity(kJ/m³) 461.7 505.7 9.5 Evaporator Glide (K) 0.45 Condenser Glide (K)0.72

Blend F offers non-flammability (according to ASTM E-681 at 60° C.)higher volumetric capacity than 1234ze-E while still achieving a low GWPrelatively to many incumbent working fluids.

Example 10 Performance of an Organic Rankine Cycle with theNon-Flammable HFO-1234ze-E/HFC-134/HFC-134a (35/16/49 wt %) Blend as theWorking Fluid Relative to Neat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASHRAE Standard 34)HFO-1234ze-E/HFC-134/HFC-134a (35/16/49 wt %) blend as the working fluidrelative to neat HFO-1234ze-E:

TABLE 11 HFO- Blend G vs. 1234ze-E Blend G HFO-1234ze-E HFO-1234ze-E (wt%) 100 35 HFC-134 (wt %) 0 16 HFC-134a (wt %) 0 49 GWP₁₀₀ 6 878.8Evaporator Temperature (C.) 90 90 Condensor Temperature (C.) 20 20 PumpEfficiency 0.65 0.65 Expander Efficiency 0.75 0.75 Superheat (K) 5 5Subcooling (K) 0 0 Pressure evaporator (MPa) 2.47 2.94 Pressurecondenser (MPa) 0.43 0.52 Pump Work (kJ/kg) 2.9505 3.4525 17.0 ExpanderWork (kJ/kg) 25.0815 25.6947 2.4 Net Work 22.131 22.2422 0.5 ThermalEfficiency 0.107 0.1053 −1.6 Volumetric Capacity (kJ/m³) 461.7 540.217.0 Evaporator Glide (K) 0.28 Condenser Glide (K) 0.40

Blend G offers non-flammability (according to ASHRAE Standard 34) andhigher volumetric capacity than HFO-1234ze-E while still achieving a lowGWP relatively to many incumbent working fluids.

Example 11 Performance of an Organic Rankine Cycle with theNon-Flammable HFO-1234ze-E/HFC-134/HFC-134a (60/10/30 wt %) Blend as theWorking Fluid Relative to Neat HFO-1234ze-E

The following table compares the performance of an ORC with thenon-flammable (according to ASHRAE Standard 34)HFO-1234ze-E/HFC-134/HFC-134a (60/10/30 wt %) blend as the working fluidrelative to neat HFO-1234ze-E:

TABLE 12 HFO- Blend H vs. 1234ze-E Blend H HFO-1234ze-E HFO-1234ze-E (wt%) 100 60 HFC-134 (wt %) 0 10 HFC-134a (wt %) 0 30 GWP₁₀₀ 6 542.6Evaporator Temperature (C.) 90 90 Condenser Temperature (C.) 20 20 PumpEfficiency 0.65 0.65 Expander Efficiency 0.75 0.75 Superheat (K) 5 5Subcooling (K) 0 0 Pressure, evaporator (MPa) 2.47 2.78 Pressure,condenser (MPa) 0.43 0.49 Pump Work (kJ/kg) 2.9505 3.29 11.4 ExpanderWork (kJ/kg) 25.0815 25.35 1.1 Net Work 22.131 22.06 −0.3 ThermalEfficiency 0.107 0.1056 −1.3 Volumetric Capacity (kJ/m³) 461.7 513.811.3 Evaporator Glide (K) 0.38 Condenser Glide (K) 0.58

Blend H offers non-flammability (according to ASHRAE Standard 34) andhigher volumetric capacity than HFO-1234ze-E while still achieving a lowGWP relatively to many incumbent working fluids.

Selected Embodiments

Embodiment A1. A method for converting heat from a heat source tomechanical energy, comprising heating a working fluid comprisingE-1,3,3,3-tetrafluoropropene and at least one compound selected from1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane using heatsupplied from the heat source; and expanding the heated working fluid tolower the pressure of the working fluid and generate mechanical energyas the pressure of the working fluid is lowered.

Embodiment A2. The method of Embodiment A1, wherein the working fluid iscompressed prior to heating; and the expanded working fluid is cooledand compressed for repeated cycles.

Embodiment A3. The method of any of Embodiments A1-A2, wherein theworking fluid is a nonflammable composition consisting essentially ofE-1,3,3,3-tetrafluoropropene and at least one compound selected from1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane.

Embodiment A4. The method of any of Embodiments A1-A3, wherein theworking fluid consists essentially of from about 1 weight percent to 69weight percent E-1,3,3,3-tetrafluororpopene and about 99 weight percentto 31 weight percent 1,1,2,2-tetrafluoroethane.

Embodiment A5. The method of any of Embodiments A1-A4, wherein theworking fluid consists essentially of from about 1 weight percent to 85weight percent E-1,3,3,3-tetrafluororpopene and about 99 weight percentto 15 weight percent 1,1,1,2-tetrafluoroethane.

Embodiment A6. The method of any of Embodiments A1-A5, wherein heat froma heat source is converted to mechanical energy using a sub-criticalcycle comprising (a) compressing a liquid working fluid to a pressurebelow its critical pressure; (b) heating compressed liquid working fluidfrom (a) using heat supplied by the heat source to form vapor workingfluid; (c) expanding heated working fluid from (b) to lower the pressureof the working fluid and generate mechanical energy; (d) coolingexpanded working fluid from (c) to form a cooled liquid working fluid;and (e) cycling cooled liquid working fluid from (d) to (a) forcompression.

Embodiment A7. The method of any of Embodiments A2-A5, wherein heat froma heat source is converted to mechanical energy using a trans-criticalcycle comprising (a) compressing a liquid working fluid above saidworking fluid's critical pressure; (b) heating compressed working fluidfrom (a) using heat supplied by the heat source; (c) expanding heatedworking fluid from (b) to lower the pressure of the working fluid belowits critical pressure and generate mechanical energy; (d) coolingexpanded working fluid from (c) to form a cooled liquid working fluid;and (e) cycling cooled liquid working fluid from (d) to (a) forcompression.

Embodiment A8. The method of any of Embodiments A2-A5, wherein heat froma heat source is converted to mechanical energy using a super-criticalcycle comprising (a) compressing a working fluid from a pressure aboveits critical pressure to a higher pressure; (b) heating compressedworking fluid from (a) using heat supplied by the heat source; (c)expanding heated working fluid from (b) to lower the pressure of theworking fluid to a pressure above its critical pressure and generatemechanical energy; (d) cooling expanded working fluid from (c) to form acooled working fluid above its critical pressure; and (e) cycling cooledliquid working fluid from (d) to (a) for compression.

Embodiment A9. The method of any of Embodiments A1-A8, wherein theworking fluid comprises from 5 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from 5 to 95 weight percent of at leastone compound selected from 1,1,1,2-tetrafluoroethane and1,1,2,2-tetrafluoroethane.

Embodiment A10. The method of any of Embodiments A1-A8, wherein theworking fluid is an azeotropic or azeotrope-like composition comprisingfrom 1 to about 98 weight percent E-1,3,3,3-tetrafluoropropene, from 1to 98 weight percent of 1,1,1,2-tetrafluoroethane and from 1 to 98weight percent of 1,1,2,2-tetrafluoroethane.

Embodiment A11. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 5 to about 95 weight percentE-1,3,3,3-tetrafluoropropene, from 5 to 95 weight percent of1,1,1,2-tetrafluoroethane and from 5 to 95 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A12. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 35 to about 95 weight percentE-1,3,3,3-tetrafluoropropene, from 2 to 38 weight percent of1,1,1,2-tetrafluoroethane and from 2 to 39 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A13. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 35 to about 60 weight percentE-1,3,3,3-tetrafluoropropene, from 10 to 26 weight percent of1,1,1,2-tetrafluoroethane and from 24 to 49 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A14. The method of any of Embodiments Al-A10 and B1-B2,wherein the working fluid comprises from 5 to about 60 weight percentE-1,3,3,3-tetrafluoropropene, from 10 to 38 weight percent of1,1,1,2-tetrafluoroethane and from 24 to 72 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A15. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from about 5 to about 95 weightpercent E-1,3,3,3-tetrafluoropropene and from 5 to 95 weight percent ofa mixture of 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane.

Embodiment A16. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 1 to about 85 weight percentE-1,3,3,3-tetrafluoropropene and from 99 to 15 weight percent of1,1,1,2-tetrafluoroethane.

Embodiment A17. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 55 to about 81 weight percentE-1,3,3,3-tetrafluoropropene and from 45 to 18 weight percent of1,1,1,2-tetrafluoroethane.

Embodiment A18. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 55 to about 70 weight percentE-1,3,3,3-tetrafluoropropene and from 45 to 30 weight percent of1,1,1,2-tetrafluoroethane.

Embodiment A19. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 1 to about 69 weight percentE-1,3,3,3-tetrafluoropropene and from 99 to 31 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A20. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 35 to about 95 weight percentE-1,3,3,3-tetrafluoropropene and from 65 to 5 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A21. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 5 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from 95 to 40 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A22. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 35 to about 60 weight percentE-1,3,3,3-tetrafluoropropene and from 65 to 40 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment A23. The method of any of Embodiments A1-A10 and B1-B2,wherein the working fluid comprises from 63 to about 75 weight percentE-1,3,3,3-tetrafluoropropene and from 37 to 25 weight percent of1,1,2,2-tetrafluoroethane.

Embodiment B1. A power cycle apparatus containing a working fluidcomprising E-1,3,3,3-tetrafluoropropene and at least one compoundselected from 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane.

Embodiment B2. The power cycle apparatus of Embodiment B1, comprising(a) a heat exchange unit; (b) an expander in fluid communication withthe heat exchange unit; (c) a working fluid cooling unit in fluidcommunication with the expander; and (d) a compressor in fluidcommunication with the working fluid cooler; wherein the compressor isfurther being in fluid communication with the heat exchange unit suchthat the working fluid then repeats flow through components (a), (b),(c) and (d) in a repeating cycle.

Embodiment B3. The power cycle apparatus of any of Embodiments B1-B2,wherein the working fluid comprises from 5 to 95 weight percentE-1,3,3,3-tetrafluoropropene and from 5 to 95 weight percent of at leastone compound selected from 1,1,1,2-tetrafluoroethane and1,1,2,2-tetrafluoroethane.

Embodiment C1. A working fluid comprising an azeotropic orazeotrope-like combination of E-HFO-1234ze, HFC-134, and HFC-134a.

Embodiment C2. The working fluid of Embodiment C1, comprising from about1 weight percent to about 98 weight percent E-HFO-1234ze, from about 1weight percent to about 98 weight percent HFC-134 and from about 1weight percent to about 98 weight percent HFC-134a.

Embodiment C3. A composition suitable for use in organic Rankineapparatus, comprising a working fluid of any of Embodiments C1-C2 and atleast one lubricant.

Embodiment C4. The composition of any of Embodiments C1-C3, wherein saidlubricant is selected from the group consisting of polyalkylene glycols,polyol esters, polyvinylethers, perfluoropolyethers, polycarbonates,mineral oils, alkylbenzenes, synthetic paraffins, synthetic naphthenes,poly(alpha)olefins and combinations thereof.

Embodiment C5. A composition suitable for use in organic Rankineapparatus, comprising a working fluid of any of Embodiments C1-C4 and atleast one other component selected from the group consisting ofstabilizers, compatibilizers and tracers.

What is claimed is:
 1. A method for converting heat from a heat sourceto mechanical energy in an organic Rankine apparatus, comprising heatinga working fluid consisting essentially of from about 1 weight percent to69 weight percent E-1,3,3,3-tetrafluoropropene and about 99 weightpercent to 31 weight percent 1,1,2,2-tetrafluoroethane using heatsupplied from the heat source; and expanding the heated working fluid tolower the pressure of the working fluid and generate mechanical energyas the pressure of the working fluid is lowered.
 2. The method of claim1, wherein the working fluid is compressed prior to heating; and theexpanded working fluid is cooled and compressed for repeated cycles. 3.The method of claim 1, wherein the working fluid is a nonflammablecomposition.
 4. The method of claim 2 wherein heat from a heat source isconverted to mechanical energy using a sub-critical cycle comprising:(a) compressing a liquid working fluid to a pressure below its criticalpressure; (b) heating compressed liquid working fluid from (a) usingheat supplied by the heat source to form vapor working fluid; (c)expanding heated working fluid from (b) to lower the pressure of theworking fluid and generate mechanical energy; (d) cooling expandedworking fluid from (c) to form a cooled liquid working fluid; and (e)cycling cooled liquid working fluid from (d) to (a) for compression. 5.The method of claim 2 wherein heat from a heat source is converted tomechanical energy using a trans-critical cycle comprising: (a)compressing a liquid working fluid above said working fluid's criticalpressure; (b) heating compressed working fluid from (a) using heatsupplied by the heat source; (c) expanding heated working fluid from (b)to lower the pressure of the working fluid below its critical pressureand generate mechanical energy; (d) cooling expanded working fluid from(c) to form a cooled liquid working fluid; and (e) cycling cooled liquidworking fluid from (d) to (a) for compression.
 6. The method of claim 2wherein heat from a heat source is converted to mechanical energy usinga super-critical cycle comprising: (a) compressing a working fluid froma pressure above its critical pressure to a higher pressure; (b) heatingcompressed working fluid from (a) using heat supplied by the heatsource; (c) expanding heated working fluid from (b) to lower thepressure of the working fluid to a pressure above its critical pressureand generate mechanical energy; (d) cooling expanded working fluid from(c) to form a cooled working fluid above its critical pressure; and (e)cycling cooled liquid working fluid from (d) to (a) for compression. 7.An organic Rankine apparatus comprising a working fluid consistingessentially of from about 1 weight percent to 69 weight percentE-1,3,3,3-tetrafluororpopene and about 99 weight percent to 31 weightpercent 1,1,2,2-tetrafluoroethane.
 8. The organic Rankine apparatus ofclaim 7 comprising (a) a heat exchange unit; (b) an expander in fluidcommunication with the heat exchange unit; (c) a working fluid coolingunit in fluid communication with the expander; and (d) a compressor influid communication with the working fluid cooler; wherein thecompressor is further being in fluid communication with the heatexchange unit such that the working fluid then repeats flow throughcomponents (a), (b), (c) and (d) in a repeating cycle.
 9. A method forconverting heat from a heat source to mechanical energy in an organicRankine apparatus, comprising heating a working fluid consisting of fromabout 1 weight percent to 85 weight percent E-1,3,3,3-tetrafluoropropeneand about 99 weight percent to 15 weight percent1,1,1,2-tetrafluoroethane using heat supplied from the heat source; andexpanding the heated working fluid to lower the pressure of the workingfluid and generate mechanical energy as the pressure of the workingfluid is lowered.
 10. An organic Rankine apparatus comprising a workingfluid consisting of from about 1 weight percent to 85 weight percentE-1,3,3,3-tetrafluoropropene and about 99 weight percent to 15 weightpercent 1,1,1,2-tetrafluoroethane.